EVENT
BOARDSIZE 19
SETUP W C17 D17 C16 C15 C13 S17 R17 Q17 O17 O18 N16 P11 P9 Q4 R3 K3 D4 
SETUP B D14 D15 D16 E17 F16 M17 O16 P16 Q16 R16 S16 R9 Q7 R5 R4 Q3 P3 
MARK \t@N16
COM
Problem 72. Black to play.  

White has just played the marked stone. What should Black do
? 
ENDCOM
B 1 O12
USER
CORRECT ANSWER
ENDUSER
COM
Correct Answer.

Black should make a shoulder hit against the white stone on the
right side.
ENDCOM
  VAR
  B 1 N17
  COM
  Failure.

  Immediately cutting with Black 1 is not good.
  ENDCOM
  W 2 N15
  B 3 K16
  W 4 P14
  B 5 R12
  W 6 K14
  COM
  White turns her stones in the center into a cohesive force with
  the sequence to 6.
  <=
  ENDCOM
  ENDVAR
W 2 M16
COM
If White follows up at the top with 2, ...
ENDCOM
  VAR
  W 2 M10
  MARK 1@O12
  COM
  Variation.

  If White responds to Black 1 by jumping to 2, ... 
  ENDCOM
  B 3 N17
  COM
  ... Black will cut at 3.
  ENDCOM
  W 4 N15
  B 5 K16
  MARK \t@N15 \t@N16
  COM
  Next, Black extends to 5, taking the territory at the top and
  leaving White's marked stones isolated from their allies below.
  <= 
  ENDCOM
  ENDVAR
B 3 N10
COM
... Black attacks with 3 ...
ENDCOM
W 4 P7
B 5 N8
COM
... and 5.
ENDCOM
W 6 R10
COM
After the exchange of White 6 ...
ENDCOM
B 7 R8
COM
... for Black 7, White will have a hard time making life for
her stones.
<=
ENDCOM